Materials Literature
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The work consists in a taxonomic survey and classification of genera of blue green algae from soil and paving, which were found in eight samplis and conducted in five stations in the Campus or Universidade Federal de Santa Maria. Twenty two genera were obtained and distributed in five families and three orders.
The quantitative analysis of the properties of domain walls in Hg 2 Br 2 and KSCN is performed using the Landau-Ginzburg phenomenological description. The domain walls in KSCN are thin and possess high internal stresses in comparison with Hg 2 Br 2 . The interactions between domain walls have opposite characters in th…
The variance of the pair correlation function, the triplet correlation function, g (3) (r,s,t), and the three-body contribution to the configurational entropy, S 3 , were studied as possible tools for distinguishing between three different models of amorphous silicon (a-Si) with (nearly) identical pair correlation fun…
We have combined a technique for the lift-off of thin diamond films from a bulk diamond with a technique for engraving diamond with a focused excimer laser to produce free-standing single-crystal diamond microstructures. One microcomponent that has been produced is a 12 tooth gear ∼400 μm in diameter and ∼13 μm thick.…
Nanocrystalline Co0.5Fe2.5O4 has been prepared by mechanical alloying and subsequent vacuum annealing. Significant increase of coercivity was observed after a postannealing at low temperatures in air. Magnetic annealing resulted in anisotropic sample with a coercivity of 2.8 kOe and a remanence of 81% of the saturatio…
It is demonstrated that controlled high-strain-rate plastic deformation of heterogeneous reactive porous materials (Nb+Si, Mo+Si+MoSi2) produces shear localization. Within the shear bands, having thicknesses 5–20 μm, the overall strains (γ≤100) and strain rates (γ̇≤107 s−1) result in changes in particle morphology, me…
We apply density-functional theory to study the expanded-FCC-to-condensed-FCC transition of a system of hard, spherical particles with a short-ranged attractive interaction, predicted recently by the simulations of Bolhuis and Frenkel (1994). Our approach is based on a non-perturbative treatment of the repulsive hard-…
Thin films of microphase separated symmetric diblock copolymers exhibit terraces. Atomic force microscopy is used to measure the free surface profile and transmission electron microscopy is used to elucidate the morphology within the film. Previous work has found the terraces to be composed of homeotropically aligned…
Abstract The rheological properties of the blend components are an important parameter in the formation of a blend morphology. The effect of viscosity ratio on the morphology of polyamide 66/polypropylene blends was studied, with primary attention to the phase‐inversion behavior and the average particle size of the di…
Abstract Dimroth and Reichardt polarity parameters E T (30) have been used, in a new approach, to quantitatively describe the swelling features due to polymer liquid interactions in binary and ternary systems. With the help of a polyurethaneimide (PUI) synthesized from polytetramethyleneglycol 650, sorption of pure li…
Abstract The morphology and the mechanical properties of polycarbonate (PC) blends with different acrylonitrile–butadiene–styrene (ABS) materials were investigated. PC/ABS blends based on a mass‐made ABS with 16% rubber and large (0.5–1μm) rubber particles are compared to blends based on an emulsion‐made ABS with 50%…
We present a theory of semiflexible polymers in inhomogeneous environments, which we use to analyze a symmetric interface between two immiscible, semiflexible polymers. Our theory reduces in the limit of small chain rigidity to the existing self-consistent-field theory of flexible polymers, but yields qualitatively di…
The size dependent electronic absorption spectra of CdSe nanocrystals have been measured in a diamond anvil cell. Under pressure, these nanocrystals are reversibly converted from a direct gap wurtzite structure to a rock salt structure which has an indirect gap in the bulk. It is thus possible to compare the influence…
Abstract Microbeads possessing amine functionality at the surface have been prepared by two methods: In the first method, poly(4‐vinylpridine/styrene) P(4VP/S) copolymer microbeads containing 13–69 mol % 4‐vinylpridine (4VP) were synthesized from the monomers. In the second method, animated polystyrene (PS) particles…
Abstract The reaction of poly(ethylene terephthalate) (PET) melts with ethylene glycol was examined in a pressure reactor at temperatures above 245°C. The reaction rate was found to depend on temperature and on the concentrations of liquid ethylene glycol and of ethylene diester groups in the polymer. A kinetic model…
Using density-functional theory we investigate several properties of Al(111), Al(100), Al(110), and stepped Al(111) surfaces. We report results of formation energies of surfaces, steps, adatoms, and vacancies. For the adsorption and diffusion of Al on flat regions of Al(111) surfaces we find the hcp site energetically…
Abstract The mechanical properties of composites of granular starch and low density polyethylene (PE) have been studied as functions of starch volume fraction ϕ, granule size, and presence of compatibilizer. Property–volume fraction relationships were interpreted using various theories of composite properties. The dep…
Heterogeneous materials, such as rock, have extreme nonlinear elastic behavior (the coefficient characterizing cubic anharmonicity is orders of magnitude greater than that of homogeneous materials) and striking hysteretic behavior (the stress‐strain equation of state has discrete memory). A model of these materials, t…
An energy functional for orbital based $O(N)$ calculations is proposed, which depends on a number of non orthogonal, localized orbitals larger than the number of occupied states in the system, and on a parameter, the electronic chemical potential, determining the number of electrons. We show that the minimization of t…
Composite sheets and nanotubes of different morphologies containing carbon, boron, and nitrogen were grown in the electric arc discharge between graphite cathodes and amorphous boron-filled graphite anodes in a nitrogen atmosphere. Concentration profiles derived from electron energy-loss line spectra show that boron a…